1. Field of the Invention
The present invention relates to a light emitting diode (LED) package, and more particularly, to an LED package not only having an excellent thermal emission properties and high durability but also with a small light loss and improved color uniformity.
2. Description of the Related Art
Recently, light emitting diodes (LEDs) are generally used as a light source for lighting or a light source for a backlight unit for a liquid crystal display (LCD). Generally, an LED package such as a white LED device outputs light of a desired mixed color by converting a wavelength of light emitted from an LED chip by using phosphors disposed outside the LED chip. For example, a white LED package manufactured by applying yellow phosphors on a blue LED chip emits a white light by mixing a blue light and a yellow light obtained by converting by the phosphors.
Since an LED package used for a light device or a large LCD device requires a white light or another mixed color light, with a great output and high quality, a package structure having an excellent thermal emission function and high color uniformity according to a far-field beam distribution is required. Also, to improve efficiency of an LED package, it is required to reduce a light loss due to light incapable of being emitted outside and returning to phosphors and a chip to be absorbed or distinguished.
FIGS. 1A to 1C are cross-sectional views illustrating conventional LED packages.
Referring to FIG. 1A, an LED package 10 includes lead frames 12a and 12b inserted therein, a package body 11 having areflective cup 11a, and an LED chip 15 mounted on the reflective cup 11a. A resin encapsulation portion 18 encapsulates the LED chip 15 in the reflective cup 11a. In the resin encapsulation portion 18, phosphors including a mixture of phosphors for converting a color are scattered.
According to the LED package of FIG. 1A, color is nonuniform according to a far-field beam distribution due to a difference between a color conversion rate of a beam vertically emitted from a top surface of the LED chip 15 caused by the phosphors and that of a beam emitted from a side of the LED chip 15 caused by the phosphors. Accordingly, entire color uniformity becomes low and quality of an output light such as lighting quality is deteriorated. To obtain uniform color, an additional color mixing element may be mounted. However, this becomes a cause of increasing manufacturing costs. Also, since an insulating body is used for the package body 11 and there is no additional heat slug structure, thermal emission properties required in a high power LED is bad.
FIG. 1B illustrates a conventional package structure provided to improve color uniformity of an output light. Referring to FIG. 1B, an LED package 20 includes a package board 24, an LED chip 25 mounted on the board 24, a resin encapsulation element 28 encapsulating the LED chip 25. A phosphor layer 26 is disposed with a certain distance from the LED chip 25. Since color is converted by the phosphor layer 26, uniformity of emitted color may be improved. However, it is difficult to stably form a phosphor layer having the structure, and a process of manufacturing the LED package is complicate. Also, due to a low reproducibility of the manufacturing process, there are shown different light output characteristics for each product. Accordingly, due to great manufacturing dispersion, it is difficult to actually apply.
An LED package 30 of FIG. 1C includes an LED chip 35 mounted on a reflective cup and a phosphor 36 disposed around the LED chip 35, which is capable of improving color uniformity. Through the phosphor layer 36 with a certain thickness, formed on a top surface and side surfaces of the LED chip 35, color uniformity of light outputted from an encapsulation element 38 is capable of being improved. However, there is a great loss of light reflected by the phosphor layer 36. In detail, since there are five surfaces where the phosphor layer 36 is in contact with the encapsulation element 38, that is, a top surface and four side surfaces, a considerable part of light emitted from the LED chip 35, which is incapable of being out of the package 30and is reflected to the LED chip 35, is scattered inside the phosphor layer 35 and distinguished, thereby causing a light loss of the package 30. Also, to obtain a structure of the package 30, a phosphor layer having a uniform thickness should be formed around an LED chip and it is required to reduce thickness dispersion between products, which requires a complicate manufacturing process and precise manufacturing conditions.